Evaluation of Lattice Defect Density in Deformed Ti by Precise Measurement of Electrical Resistivity

Several metallic materials have been developed for many purposes by alloying and controlling microstructure. From the viewpoint of materials recycling, several properties should be controlled by the latter in simple alloys. Then, observation and evaluation of lattice defects such as vacancy, dislocation and grain boundary are very important for understanding microstructure development during thermo-mechanical treatments. The purpose of this study was to establish a method for esti-mating density of lattice defects in cold rolled and annealed Ti by a precise measurement of electrical resistivity. Pure Ti plates were cold rolled at room temperature. Bar shaped specimens were cut from the plates. Electrical resistivities at 77 K (liquid nitrogen) and 300 K were measured by a direct current four-point method with a constant current of 100 mA. The accuracy of temperature control at 300 K was 0.1 K in silicone oil. Basically the electrical resistivities gradually increased with increasing a reduction of thickness. The density of dislocation was determined to be 2–8 × 10 14 m − 2 in the 15–80% CR specimens